Latin and German form of John [q.v.], from Hebrew "God has been gracious".
Ioannes, Iohannes, Joannes and Johannes are all Latin forms of John and its derivatives, used in old documents with appropriate Latin case endings.
Johannes is also the Latin form for Evan, the Welsh form of John.
A correspondent [CS] has sent a note of a Will registered 1855 in Fochabers, Bellie parish, Banffshire, Scotland for "... Johannas Y---, Merchant ..." who was registered as James on his death certificate and as witness to a birth in 1830 [IS]. Another correspondent [AB] has noted that the family were members of the Roman Catholic church.
We have no other reference to a Johannas being Latin for James. Johannes is the normal Latin for John.